US1291990A - Two-wire rotary-connector telephone system. - Google Patents

Description

T. G. MARTIN. Two wlREVRoTARY CONNECTOR TELEPHONE SYSTEM.

T. G. MARTIN.

TWO WIRE ROTARY CONNECTOR TELEP HONE SYSTEM.

APPLICATION FILED ocT. II. 1909. IIEIIEwED JUNI: 1. 191s.

Patented J an. 2l, 1919'.

3 SHEETS-SHEET 2.

. T. G. MARTIN. TWO WIRE ROTARY CONNECTOR TELEPHONE SYSTEM. APPLICATION FILED ocr. II| 1909. IIEIIEwED JuIII: 7, 191s.

Patented Jan. 21, 1919.

3 SHEETS-SHEET 3.

Aoffz' UNITED sTATEs PATENT OFFICE.'

TALBOT G. MARTIN, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELCTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TWO-WIRE ROTARY-CONNECTOR TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Jan. 21, 1919.

Application led October-11. 1909, Serial No. 522.065. Renewed .Tune 7. 1918. Serial No. 238.795. f

To all-whom z't may concern.'

Be it known that I, TALBOT G. MARTIN, a citizen of the United States 0f America, and

resident of Chicago, Cook county, Illinois,

change systems in general, but more particu-` larly to automatic or semi-automatic exchange systems, and especially to systems in which provision is made for controlling automatic switches, such as selectors and connectors, over metallic line circuits.

For certain broader purposes of my invention the talking current may be supplied either from a common battery or from local batteries at the subscribers7 stations. `Also, for the broader purposes of my'invention the first selectors may be employed on a percentage basis or as individual switches for the subscribers lines. I have, however, elected to illustrate my invention in connection with that specific form'of automatic telephone exchange system in which common battery means an employed for furnishing the talking'current. and in which the first selectors are employed on a percentage basis. With this arrangement, as will hereinafter more fully appear, means are provided for automatically selecting idle first selectors. In this way each calling= sub- Iscriber does two things before operating the first selector and other numerical switches in :wcordalicc with the called number. First, the calling line is automatically connected with a preselected idle trunk leading to an idle first selector; second, another idle trunk is selected for the subscriber who makes the next call.l Thus each calling subscriber obtains connection with an idle first selector through the medium of a preselected trunk As herein disclosed, these switching operations are all lcontrolled by the calling subscriber over metallic line circuits. In other wordsyno operating grounds are ernployed at the substations of the system.y

'In the practice of automatic telephony it, has often been found desirable to give a subscriber more. than onetclephone line, or

to providea plurality of trunk lines leading to a private branch exchange. In such case means are provided for automatically selecting an idle one of the said telephone lines, the same all being glven the same number, inasmuch as any one of these lines Will serve the purpose of the calling subscriber.

'I his is also true where a number of trunk lines are provided for a private branch ex-A change, as in such case a calling subscriber is satisfied to obtain connection with any one of said trunk lines. These trunk lines all have the same number, and if one or more of them are busy it Will serve the purpose of any calling subscriber to obtain connection with any one of the remaining idle trunk lines. For this automatic selection of an idle one of a number of telephone lines, or of an idle trunk line, it has been the practice, to employ what are ordinarily known as rotary connectors-that is to say, connectors which are capable of rotating automatically in one or more or even all of the bank levels thereof, very much as a selector automatically rotates to find an idle trunk line. There is, however, this difference between the automatic selective operation of a rotary Vconnector and the similar automatic selective operation of a selector.

In a selector the wipers are raised step by step to the desired level under the control of the calling subscriber. or of an operator.

When the wipers of the selector reach the predetermined level, they then automatically rotate in that level, without the necessity of any further act on the part of the calling subscriber. until an idlc trunk line is found. In a rotary connector, however, the wipers thereof, when raised tothe desired level` do not at once commence rotating inl that level,

but to the contrary remain opposite that particular level of bank contacts until made to proceed in a rotary manner by some further act on the part of the calling subscriber. For example. a selector is responsive to the impulses for only one digit of the called number. These impulses raise, the wipers of the selector to thel desired level, and without the transmission of any further impulses llO that these contacts are arranged in levels, each level containing ten sets of bank contaets, to each of which one line is allotted.

In this case it is assumed that the second level of the second selector banks are provided with trunks to rotary connector switches similar to those shown in Fig. 2, while the trunks from the fourth level ter- Ininate in connector switches similar to those shown in Fig. 3. Trunks from the remaining levels terminate in connectors, as yshown in Fig. 3, but said connectors have no automatic rotary selective operations. 1

The substations may be of any suitable or approved type. As shown, it will be seen thatv substation A is arranged to operate in connection with a two-wire system-that is, a system in which no ground connection -is used at the subscribers substation. Substation A, for example, comprises the usual receiver 2, switch hook 3, induction coil 44 which consists of the primary winding 5 and secondary winding 6, transmitter 7, condenser '8,y ringer 9, and impulse wheel 10 which has the usual impulse teeth 11. The impulse wheel 10 is secured to the shaft 12, to Whichshaft there is also secured the dial (not shown). vAs the dial returns to normal position after being rotated to call a digit the impulse teeth 11 are adapted to engage the cam 13 upon the end of the spring 14, and thereby ca'rry the latter out of engagement with the spring 15. Upon the switch hook 3 there is the cam arm 16 which, when the switch hook is up, permits the springs 17 and 18 to engage, thereby bridgingacross the'subscribers line conductors 19 and 20 the primary circuit including the transmitter 7 in series with the primary winding 5; but when the switch hook is lowered the spring 17 is carried out ofengagenient with thet spring 18 and into engagement with the spring 18, whereby vthe ringer 9, in series with the condenser 8, is bridged across the line conductors 19 and `20 instead.

The line switch C may be of any suitable or approved type. For instance, it may be a modified form of the line switch disclosed in British Patent No., 26,301 of 1906, and described in the American Telephone .lournal of Chicago, Illinois, of June 6, 1908.- In its'general form it comprises a trip magnet 23, a release magnet 24 and a bridgecut-ff relay 48; The trip magnet 23 is designed to operate the usual plunger for pressing the bank springs and 36, 37 and 38. 39 and 40, and 41 and 42 into engagement.' This plunger is soarranged that when in normal position it is under the control of the master switch J, whereby the said plunger may always be removed from opposite busy-trunk to a position opposite an idle trunk. The release magnet operates to restore the plunger to normal position.

switches, usually one hundred, always holdihe motor magnet is denergized.

The bridge-cut-otf relay 48 operates to shift the springs 49 and 52 out of engagement with the springs 50 and 51, respectively.

The master switch I may be of any suitableor approved type. For instance, it may be a modified form of the master switch described and illustrated. in the said lmcrican Telephone Journal of June 6, 1908. In its general form it comprises a motor magnet 53, a motor magnet relay 56, the circuitopening relay 25, ratchet wheel 55, interrupter whepl 54, master switch bank Q, wiper 58 and condenser 27. The switch yshaft controls the plungers of several line ing them' in readinessto engage an idle trunk. Thls part1cular master switch 'shaft f has a step-by-step reciprocating motion, and

all idle plungers are held in locking engagement with said shaft. The plungers of the line switches, as described in the publication mentioned, are not self-alining-that is, a plunger does not automatically come into locked engagement with the shaft until the master switch shaft again resumes the original position where the plunger was tripped. When one line switch operates, its plunger is tripped and engages the springs of the bank terminals of an idle trunk. The motor magnet relay 56 is accordingly energized. This relay operates to close the motor magnet circuit and the circuit of the relay 25. The motor magnet operates to rotate the ratchet wheel and intcrruptcr wheel. When the ratchet wheel is rotated 100 one'notch the interrupter wheel has'rotated enough to close the springs 21 and 22, which keep the motor magnet operating until the idle plungers are directly opposite the bank terminals of an idle trunk. lVhen this position is reached the springs 21 and 22 separate, and as the master switch wiper 58 has been moved' to a position on the master switch bank corresponding to an idle trunk.

Thilo the motor magnet is operating, the circuitopening relay 25 is energized. thereby shifting the spring 32 out of engagement with the spring' 33 and into engagement with the spring 34. In this way all the trip magnets are disconnected from the battery lead and connected to the busy-signaling current similar to the busy-signaling current furnished by the apparatus I in Fig. 2, thus preventing thc selection of a busy trunk and giving a subscriber the busy-signal if all the trunks are busy.

The first selector switch shown at D is an improved form of the selector described in United States Letters Patent No. 815,321, granted March 13, 1906, to Keith, Erickson andv Erickson, and is adapted to operate in connection with a two-Wire system. Among other details it embodies the following fea'- tures: The'switch shaftgtnot shown)- carries 130 the vertical and rotary 'Wipers 81- and 82,

rotary magnet wiper, respectively. The

.side switch is under the control of the private magnet 88, and when the side switch is in norma-l or first position the wipers 841, 85, 86 and 87 occupy the contact points 89, 90, 91 and 92, respectively. ln the second position the 'wipers rest on the Contact points 93, 0l, and 96, respectively; and in third positionthe contact points 97, 98, 99 and 100 are engaged by their respective wipers. The windings ofi the usual vertical and rotary line relays are, in this case, conii bined into one double wound relay 101 coniprising the winding 102 which is connected with the battery lead 103, and also with the vertical line trunk conductor when the side switch wiper 811 is in lirst or second posie tion. The second winding 10st is connected to ground, and also to the rotary line trunk conductorwhen the side switch wiper 85 is in first or second position. medium of this double wound relay, and while the side switch isin first position, the subscriber controls the yer-tical" magnet 105, which operates to raise the switch shaft and wipers S1, 82 and S3 vertically. This line relay 101 also controls the private magnet relay 106,Which latter in turn controls the private magnet 88. r1`he private magnet, as

usual, controls the side switch. `While the side switch is in second position the rotary magnet 107, which operates to carry the switch shaft and wipers 81, 82 and S23 in a rotary direction, is energized. 'lhe release magnet 108 provides ineens for restoring the selector switch to norinal position. .Upon the switch shaft, which carries the wipers 81, 82 and 8S, there is mounted the arm 109 which., when the shaft is raised one or incre steps, permits the soring 110 to engage the contact point 111, wherehythe release inagnet 108 is connected to the battery. The release relay 112 provided for closing the energizing circuit of the release magnet 108 after the switch is operated. The hackA` release relay 113 is provided or opening),A the energizing circuit through the release inamet 2-1 of the line switch. The relai's 106, 112 andk 113 are slow-acting,l relaysthat is, they are so provided with a copper shield that when energized, and the energizing circuit then broken, the said relays remain for a moment in an operated position. ln other words, they do not instantly return to normal position after the ener. ,ing circuit is breiten. Y

Theseeond selector lli is similar to the first selector l), and is provided with the lrenal double-wound line relay 114s hailing;

Through the vselector switch.

asettico the windings 115 and 11G connected with the vertical and rotary side switch Wipers 117 and `118 in the saine manner in which the windings of the relay 101 of the selector switch D are connected. 'to their vertical and rotary side switch wipers.

Since like parts are similarly represented, the rotary magnet 119 and Vertical magnet 120 will he recognized and understood. The release magnet 121 is operated in the saine manner in connection with the svitch .l that the release magnet 108 is operated in lhe private connection with the switch l). magnet is controlled hy the privato niag net relay 123. The release rel ay 124i out the second selector switch if) performs the sanie function in connection with this switch as the release relay 112 and the rhaelt-release relay 113 perform in connection with the first selector switch `1)-that is, the springs controlled hy the relays 112 and 113 are so arranged in the second selector switch E that they are controlled hy a central relay 1211. ln the switch E the relays 123 and 124i. are so arranged that they denergize slowly, thc same as the relays 106, 112 and 113 oit the selector switch D.

The rotary connector switch li an imV proved forni of the connector switch disclosed .in United States Letters latent No. 815,176, granted Merch 1?, 1906, to Keith, Erickson da ldlriel-son. in this rotary connector F means are provided whereby the shattniay he automatically rotated, like the shaft of the selector switches, when the privatewiper engages a lousy Contact, and also whereby it is adapted to operate in connection with a two-wire coniinon battery system. The connector switch shait (not shown), like the shaft of the selector, carries the line wipers 125 and 126 and the private Wiper 12T. The connecter switch is also controlled by the calling subscriber through the medim um 'of' a double-wound line voley .lhe line relay 128 is provided with the windings 129 and 130. @ne terminal otl the winding 129 is connected to 'the battery lead, while the other terminal is connected with the rertical trunk line conductor 192. The windn ing 12E-0 is connected with ground and also with the rotary trnnl; line conductor llhis line relay directly controls the 'rertical magnet 1551, rl'he purpose of the vertical magnet 131 is to gite the shaft and shaft wipers a .ertieal motion, and the rotary magnet 132 imparts to the shaft and shaft wipers a rotaryor circular motion. The connector switch is also provided with the slow-actinggl release relay 15.3, which is similar to the release relay 1211 of the rllhe pr' iet r l y as usual, controls the p which latter. onder eert ,in conditions, con trois the rotary inegnct 132 and cleo the side switch Wipers 136, 137, 138, 139 and 140. The private magnet 135, as arranged to operate in connector switch E, plays a very important part, and controls therotary action to a great extent. The ob]ect 1n providing the connector with this automatic seactive feature is as follows: Abusiness house r private branch exchange, for example, iay be providedhwith three lines,all of which are given the saine number; and it ,nay become desirable to so arrange the system that if one line is in use, the calling switch will automatically extend the calling subscribers line into connection with the second line; if the second line is also busy connection may be carried to a third line, and so on.A The calling subscriber would, of course, have no control over the apparatus as to which one of the lines he makes connection with. rIIhis, however, does not concern him, since any trunk line to the said oiice or private branch exchange will serve his purpose. The arrangement of the connector banks themselves will be as follows: If the oiiic'e at which the number 2221 is located wishes three telephones it will be given three lines, one terminating in the irst contact of the second level of the connector banks, and the second in the second contact of the second level. etc. Now, if the number 2221 is called, the connector is raised' to the second level and then rotated into engagement with the trsteontact of the second level; but if the said contact is busy the connector is automatically rotated onto the second set of contacts. It becomes desirable, of course, to provide means for notifying the calling subscriber in the event that all the -trunk lines are busy. Forv this purpose a fourth set of bank contacts of the second level are connected with a busy-signaling circuit, at which contacts the connector' must stop in the event that all lines are busy. A busy-signaling current is then sent to the calling subscribers line over a,circuit including this fourth set of contacts of this level.- This arrangement, however, is not coniined to any particular level, as any level may be divided in the sameway, and any subscriber may thus be given any number of lines, depending on the number of contacts in each level. The back-bridge relay 141, comprising the windings 142 and 143, provides means. whereby the called slibscriber is provided with battery current for talking purposes. Ashere shown, the connector switch has provision .for automaticl ringing-that is, the signaling of the called subscriber is not dlependent upon the calling subscriber-.pressing a signaling button, but as soon as connection is estz'lblishedwith the desired line the interrupter 144 intermittently closes an energizing circuit through the ringer relay 145, whereby the terminals of the ringer generator H are intermittently bridged across the normal conductors of the called line. The relay 146 is arranged in the private wiper circuit, and when the said'wiper engages the busy contact an energizing circuit is closed through this relay 146, which operates to close an energizing circuit through the private magnet 135. The means ,whereby the connector switch may be restored to normal position consists of the usual release magnet 133HL which, when the connector switch shaft is raised one or moresteps, is connected to the battery lead through the normal springs 131a and 1321. By means of the condensers 147 and 148 the circuit through the conncf tor switch is divided into two sections. IThe busy-signaling apparatus I comprises the interruptor 149 in series with the winding 150 of the inductioncoil 151. The inding 152 is connected with the spring 1 3,' and when the relay 154 energizes, as will be explained, the busy-signaling apparatus 'is connected with the connector switch wiper 126.

The connector switch L shown in Fig. 3 combines the automatic rotary feature of the connector F'with the ordinary features of asimple connector. The connector L is so arranged that if the wipers are broughtinto engagement with a busy line on certain levels, said wipers remain on the terminals of that line, the side switch becomes locked in second position to prevent the calling line from being extended into connection with the busy line, and the calling subscriber is given the busy-signal.l If, however, the wipers arc brought into contact with a busy line on certain other levels, the said wipers are then automatically rotated onto an idle line in a manner` similar to that of the connector F. On to vof the frame of the connector is mounte( a group of springs (292, 294, 291, 293 and 295) which is adapted to be operated by the arm 289 which is attachcd to the top of the switch shaft. As v long as these springs are in normal' posi- -tion-'that is, with the spring 293 in contact after the shaft has been raised high enough to force' the springs 293 and 292 into the position shown in Fig. 4 the connector then' operates like a rotary connector. By changing l(he length of the bushing on the end of the spring 293 the connector L may be made rotary on as many levels as desired. For example, if it is desired to provide two rotaryl levels the bushin on the spring 293 may be made of such ength as to be engaged by the arm289 only after the shaft wipers are raised above the eighth level. Each of the bank levels that is engaged bv the wipers before the springs 292 and 293 are operated can accommodater ten single subscrihers` while each level which is engaged by the wipers after-said springs are operated 'can accommbdate' one or more groups of lines7 all the lines of each group being accessible by calling one number. This division of bank contacts into groups is the saine as explained for the connector l?, the last con liacts of each group beingd connected to the busvsigualing machine l. rilhe connector L is also provided with a relay 278 for the purpose of connectingI the ground interrupter 279 with the rotary magnet 269 under certain conditions, as will hereinafter appear. V

The ope'rationAoi the system may be more lclear-ly dis'closetrii.E cachet-en, during the process "ot a call, is followed up in detail. 1t will be assumed that the substation i Wishes to call the otiice which is registered as 2221 and which is provided with the substation A and A3, of which only substation A is shown.

To'call the number 2221 (substation A, Fig. 2) the subscriber at substation A (Fig. l) removes his` receiver` from the switch hook and operates the calling device for each digit of the called number, in the Well-imown nrannerwthat is, when the receiver is re moved from the switch hook a preliminary impulse provides an energizing circuit for the trip magnet 23 of the line switch.v C, Wherebg7 the line switchA C is operated to seize an `dle trunk line leading to a first selector switch. The dial is turned for the first digit, and upon returning to normal position operates the first selector switch to establish connection with an idle trunk line y leading to a second selector switch. in a similar manner the dial,` upon returning to normal position tor the second digit, operates the second selector switch E to establish Vconnection with an idle trunk line leading to a connector switch. The impulses delivcred`by the dial for the last two digits are directed toward the 'connector F, which opcrates to place the shaft Wipers in lconnraftion with the contacts corresponding to the desired oiiice. The preliminary impulse for energizing the trip magnet 23 occurs when the receiver 2 is removed. from the switch hook, 3, and the cam arm 16 permits the spring 17 to engage the spring 18, therebyY removingF the ringer from across the line and bridging the primary circuit instead. Vvhen the primary circuit is thus bridged across the line, the 'energizing circuit for the trip magnet 23 is `completed and extends from ground G through the springs 50 and' `lqmrotary line conductor 20, through the springs 17 and 18, impulse springs 15 and 14, primary Winding 5, transmitter to the vertical line conductor 19, springs 52 and 51, through the ivmdlng of the trip magnet 23, springs 32 and 33 of the clrcuit--opening` ren lav 2o to the battery lead 15'?, thence through lN-tr" Bt i n abili )at ely o gi oun its lsoon as t e tup magnet v23 energiaes, the piunger arm is 'tripped and the plunger' engages the bank terminai springs et an idie trunk, as preiracheno viously described. `When the bank contacts are thus closed, the line conductors 19 and 20 are cut through to the trunk line conductors and 7d, whereby the line relay 101 of the selector D isenergized. This circuit extends from ground G5 through the Winding 10ste?? (he double-wound line relayY 101, contact point 90, side ,switch Wiper S5, trunk line.- conductor 7G, springs 38 and 37, line coin ductor 20, primary circuit of substation fr, line conductor 19, springs 35 and 36, truid line conductor 75, side switch Wiper 8e, con tact point 89, winding 102 et the relay 101 to the battery lead 157, thence through ba' tory B to ground G. The line relay 101 upon energizing operates to disengage the springl 161 from the spring-166 and to place it in contact with the spring 162. The former action clears the release trunk 77 of the ground GG, which prevents the release magnetV 21 of the line switch Jfrom energizing; the latter action establishes an energizing circuit throughthe release relay 112, said ycircuit extending from ground G6 through springiiA and into engagement with the spring 165. This is the condition of the tiret selector D when the subscriber operates the dial for the first digit. Furthermore, when the bank springs 39 and 40 are'closed in eontact, after the line switch plunger-trips,thel bridge-cutoff relay L18 is energized over a circuit extending' from ground Gr through said bank springs, hridgecut-olf relay 48 to the battery lead. The relay operates, fore innl the springs 49 and 52 out of engagement with the springs 50 and 5l, clearingthe line conductors of the line switch circuits. The engagement of the bank springs 39 and il) also provides a guarding potential over the private normal conductor 80 to the connector bank terminals corresponding to the line of the calling subscriber to prewnt another subscribed from callingthe said line after the c'allingsubscriber at' substation A yremoves his receiver preparatory to making' a call. VJhen the bank springs 4:1 and i2 are closed in contact an energizing circuit is esl'alilishcd through the motor magnet relay :36 et the master switch J., it being undersl'oodthat the ground connection G to the release trunk 77 at the selector D is removed almost instantaneously. Said energizing circuit extends from ground G2 through the motor magnet relay 56, common segment 57 of the master switch bank Q, Wiper 58, individual segment (50, bank springs 42 and 41, release magnet 24 to the bittteryiead 15'1f thence through battery B to ground G. li' will be seen that the motor magnet relayv and release magnet 211- .are both included in this circuit; bnt the den of current is not sufficient to operate the magnet while the relay is operated, closing the motor magnet kcircuit'and the circuit of the circuit-openthrough thecircuit-openine relay 25, interrupter springs 70 and'71, re ay springs 72 and 73 to the battery ltlad.l The relay 25 is slowacting-that is, slow to denergize, and thus remains in an opcratcdicondition while the motor magnet is operating, the intcrruptcr .springsvg70` andi-,71 being intermittently opened; The"circuit-opening relay`when -operatcd' disconnects the lbattery lead from allA trip magnets in the group,"thus making it'impossible for a trip nii'agnet to release a .plungerwhile the c-1rcu1t of the motor magnet and relay 25I is closed. The circuitopening relay 25 when operated also shifts thel spring 32 into engagement with the spring 31, thus connecting the trip magnets to al source of busyfsignalingcurrent. The motor magnet operates as a buzzer by means` ot the springs`70 and 71, successively energizing; and denergizing, to advmice the ratchetl wheel 55 and the'interrupter wheel 54. which in turn advance theshaft and all idle plungers that are in lockipg engagement with the shaft to a position opposite the next idle bank terminal. As soon asthc motor magnet advances the ratchet wheel one step, the auxiliary springs 21 and Q2 'close in contact. thereby establishing the energizing circuit of the motor magnet 53'aud the relay 25 independently of the motor magnet relay 56. lVhen the wiper 58 leaves the individual contact 60, ii' the next individual contact is not guai'ded by a battery potential. the motor 'relay 56 will be deiincrgizcd. However. theI motor magnet will continue to rotate t-he ratchet wheel until the idle plungcrs are in a position directly in trout ot the waiting idle trunk. This is accomplished by the springs Q1and` 2 (which are arranged in multiple with the springs 72 `and 73) making contact until toi-ced apart by the interrupter cam wheel 5.4. It will be seen that to give this condition the interruptor wheel 5l must be set in a position to operate these springs Q1 and 22 according to the relative `position of the idlc plungers. lt will be understood. ot course. that the line switch bank terminal shown corresponds to the first segment of the master switch bank Q. and therefore corresponds-to the trunk line conductors 75, 76 and 77 which terminate in the selector D. The master switchwill accordingly come to rest in a position where the plungers are directly in front of an idle trunk terminal.

y The first digit being 2. the impulse spring 14 is twice carried out of engagement with Ainto engagement with the first contact of the impulse spring 15. As a result the encrgizing circuit through the line relay 101.is broken twice, and the spring 161 comes into contact with the yspring 166 twice. After the two impulses are thus delivered the liuc relay 101 again energizes and carries the spring 161 into contact with the spring 162. As previously explained, the relay 112 is a slow-acting relay-that is, slow to delinergize; and when this energizing circuit is momentarily broken duririg the vertical im pulses just delivered, the said relay does not denergize, but remains in an operated posi.- tion rwith the spring 163 in contact with the spring 165. Then when the spring 161 engages the spring 166 two impulses are transmitted to the vertical magnet 105.

the springs 161 and 166 to the springs 163 and 165, through the private magnet relay 106. through the winding of the vertical magnet 105, contact point 92. side switch wiper 87 to the battery lead 157. thence through battery B to ground G. Two impulses being delivered, the vertical magnet 1 05 is thereby energized twice. and the shaft wipers are given two vertical steps in the .well known manner. It. will be seen that the private magnet relay 106 is included in the energizing circuit ot the vertical magnet 105. l This relay also energizcs. but being a slow-acting relay, it energizes on the rst impulse and remains so until all the inipulses are transmitted. This relay. upon energizing. operates to close thc. springs 167 and 168 in contact. whereby an energizing circuit is established'through the private magnet4 88. This circuit extends troni ground G through the springs 167 and 168, private magnet 88l to the battery lead 157, thence through battery B to ground G. The private magnet relay 106 deiuergize-s after the last-vertical impulse, since this'energizing circuit is no longer maintained after the springs 161 and 166 disengage. Hence. the said relay denergizes. permitting thc springs 167 and 168 to disengage. whereby the energizing circuit through the private magnet 88 is in turn broken. which private magnet now deiinerv gizes and permits the side switch to pass from first to second position. permitting the side switch wipers S6 and l87 to engage the contact points and 96. respectively. The closure of contact between the side switch wiper 87 and the contact point 96 sets up an energizing circuit for the rotary magnet 107 vfrom ground G5 through the interruptor rotary magnet then operates to rotate HB shaft wipers 81. 82 and 83 of the selector f second position.

the second level oi the selector banks, from vwhich contact it is assumedthe trunk line conductors 170, 171 and 172 lead to the second selector switch E. lr' the first trunk i is busy, however, and the wipers have to pass over busy contacts, then as soon as the private wiper S3 engages the first private hunk contact, the private .magnet 88 again energizes, locking' the side switch in The energizing` circuit 'for said private magnet extends from vthe grounded terminal G of the ybattery B through the switch of the busy trunk, through the private Wiper 83, thence through 'the conductor 173 to the side switch Wiper 536, Contact point 95, through theV winding' of the private magnet to the battery lead 157, thence through. battery B to ,Q'round G. The private magnet S8, upon thus becoming energized, locks the side switch wiper 87 in engagement 'with the contact point 96, whereby the rotary magnet 107 will be energized step hy step until the wipers are carried onto the first idle trunk line. At the .instant that the private wiper leaves the last husy contact point the energizingu circuit through the private magnet S8 is destroyed.

and, a result the selector si deswitch passes to third position. 1f, however, there are no lousy trunkA lines the-*private magnet 88 releases the side switch to third position, in the weil known manner, as soon as the wipers are carried into engagement with the first trunk line. As soon as the side switch passes to third position, iis-stated, the subscribers line conductors 19 and 2O are' exf circuit was established through the line revlay 101 or' the selector D when the subscribers line conductors 19 and 20 were eX- tended through the line switch bank to the trunk conductors 75 and 76. The relay 114, upon energizing, operates to shift the spring' li'from the spring 175 to the spring 176. I

W'hen the springs `174 and 176 engage, an erre'rgiziru'gv circuit is established through the release relay 124. This circuit extends from Aujrourui if?? through the springs 17 1 and 176, through the relay 124, to the battery lead 157, thence through battery .ll to ground G.

Vllhe relay, upon energizing, operates to shiftv the spring;r 177 'from the spring- 178 to the i spring 179, and the springs 180 and 181 are alsoclosed 'in contact.. This operation of the second selector switch loccurs at the 'instant that the side switch Wipers 841 and .tacts (not shown) naeneee 85 of the selector switch D pass to third position and extend the subscrihers line conductors 19 and 20 to the second selector switch E. When the second selector' switch therefore thus operates, a guarding potential is established at the private multiple contacts for iroteeting the seized trunk line conductors 110 and 171 against seizure ley another calling first selector. This guarding potential extends from ground Gr8 to the Contact point 182, side switch Wiper 188, through the springs 181 and 180, conductor 172 to the contact engaged by the private wiper 83, and to the private multiple eon- Furthermore, when the first selector switch D operates, and the side switch passes tothird position, anew ener- ,sizing circuit is established through the release relay 112. This energizing circuit extends rom ground GS at the selector switch E through the springs 181 and 180, con ductor 172, shaft wiper 83, conductorrl, through the side switch wiper 86, Contact point 99 and the relay 112 to the battery lead 157, thence through battery 'B to ground Gr. The relay 112 thus remains in an operated position with the spring 163 in engagement with ythe spring 165, but the line relay 101 returns to normal position when the side switch wipers Se and 85 en` gage the contact points 97 and 98, respectively. The energizing' circuit through the line ,relay 114: extends from ground G through the winding 116 to the-side switch wiper 118, thence through the conductors 171 and 76 and line conductor 20, throughr the primary circuit of the substation, through the verticalline conductor 19, thence through the trunk conductors 75 and 170, side switch wiper 117 through the Winding 115 of the relay 114 to `the battery lead 157, thence through battery B to ground Gf. "When the dial returns te normal position for the second digit 2 this circuitthrough the line relay 114 is interrupted twice, when the impulse spring 111 is carried out of engagement with the spring 15 by the impulse teeth on the wheel 19. The circuit'being interrupted twice, the said relay 114 mo mentarily7 denergizes, thus permitting' the by an energizing circuit is completed through the vertical magnet 120, extending from ground G7 to the springs 174 and 175, springs 177 and 179, through the winding of the private magnet relay 123, through thewinding of the vertical magnet 120, con'- tact point 184C, side switch wiper 185 to the battery lead 157, and through battery B 'to ground G. The private magnet relay 1231,

`spring 17a to engage the spring 175, Wherel heilig included in this circuit, energizesgand since it is a slow-acting" relayit remains in an operated position until the last vertical impulse is delivered. vAfter the two. iinpuises are thus deiivered, `the relay 111 l'with the spring 201, and thc again energizes and carries the spring 174 into contact with the spring 176, whereby the circuit through the private magnet relay and the vertical magnet 120 remains open. When the relay 123energizes, the springs 186 and 187 arepressed into contact, thereby causing an energizing current to flow through the private magnet 122, said circuit extending from ground G7, through the springs 187 and 186, through the winding of the private magnet 122 to the battery lead 157, thence'through battery B to ground G. lVhen the relay 123 denergizes and breaks the energizing circuit through the pri 'ate magnet 122, the private magnet also -denergizes and permits the side switch to pass from first to second position. When the side switch wiper 185 passes to second position and into engagement with the contactpoint 188, an energizing circuit is established'through the rotary magnet 119 which now operates, as explained in connection with the rotary magnet 107 of the selector switch D, to select an idle trunk line leading to the connector switch F. After the switch coines to rest with the side switch in third position, the shaft wipers 189, 190 and 191 are in engagement with the trunk conductors 192, 193 and 194, respectively, which lead to the connector switch F (Fig. 2). At the instant that the wipers 117 and 118 pass to third position and into engagement with the contact points 195 and 196", the subscribers line' conductors are extended to the connector switch F, and an energizing circuit is established through the line relay 128 in the saine manner in which the energizing circuit was established through the line relay 11-1` of the selectoi switch E when the side switch wipers ot' the first selector passed to third position. They energizing circuit through the line relay 128 extends from ground GW through the winding 130, trunk conductors 193, 171 and 76 to the line conductor 20, thence through thc sub-station to the vertical line conductor 19, trunk conductors 75, 170 and 192, thence through the winding 129 to thc battery lead 157, and through battery B to ground (l. The line relay 128. upon energizing, operates to shift the spring 196 from the spring 197 to the spring 198, whereby an energizing circuit is established through the rcleasc rclay 133 extending from ground (irl through the springs 196 and 19S, relay 135% to the battery lead 157, thence through battery B to ground .(1. 'hcn the relay 321 encrgizcs, the spring 199 is shifted out of engagement with thc spring 200 and into engagement spring 202 is shifted into engagement with the spring 209. This primary operation of the connector relays 12S and 1321 occuis at the instant that the side switch wipers 117 and 11S ot' the selector E pass to third position and extend side switch potential for protecting the trunk line con- y ductors 192 and 193 against seizure byanother second selector. This potential extends fioni ground (i12 to thc sideswitch wiper 139, springs 203 and 202, conductor 191 to the private bank contact engaged by the private wiper 191, and to the private multiple contacts (not shown). Furthermore, when the side switch ctv-the second. selector E passes to third position a new en,- ergizing circuit is established through the release relay 124, said circuit extending from ground G12 at the connector switch to the conductor 194, through the shaft wiper 191, side switch wiper 20-1, contact point 205, through the release relay 124 to the battery lead 157, thence through battery B to ground G. Also, this saine guarding potential established at the contact engaged by vwiper 191, side switch wiper 201, contact point 205, contact' point 206, si'dc switch wiper 183, springsl 181 and 180, conductor 172 to the multiple private bank conta'ets of the irst selector switches. The cnengizing circuit of the release relay 112 f thc selector D is also extended to the connector F;

, this circuit, like the one last traced, extends to the conductor 172, thence through thc private wiper 83, conductor 173, side switch wiper S6, contact point 99, relay-112 to the battery lead 157. 'The opeijation of the dial for the last two digits affects the connector switch, and when thc dial is operated for thc third digit 2 thc impulse spring 1-1vis twice carried out of engagement with thc spring 15, thereby momentarily 'dcenelgizing the line relay 12h twice, whereby the spring 196 twice engages the'spring 19.7` thus sending two impulses to the vertical i'nagnct 131 troni ground (1, through the springs 196 and 197, springs 199 and 291, through the vertical magnet 1211...(-oiitact point 207. side-switch wiper 1-10 o thc battcry lead 157. thence through battery l 'to ground (i. 'l'hc vertical magnet. upon lcing energized. operates` one slcp at a time to carry the shaft. wipers 125. 126 and 127 two steps to a point oppositil the second lcvcl.

'hcn the liuc relay 12hl thus operates. an

the spring conductor 208, through the private magnet rela 134 to the battery lead 157, thence through battery B to ground G. The relayv 13.4 energizes and Ashifts `the spring 209 out of engagement with the spring 210 'and into engagementv wit-li the spring 211; also, the spring 212 is shifted into engagement with 213. When the springs 212 and 213 engage, an energizing circuit is established through the private magnet 135 from groundGr13 through the springs213 and 212, private magnet 135 to the battery lead 157, thence through battery B to ground G. The relay 134', being a slow acting relay, remains iii an operated position while the verticalA V impulses arebeing sent; but after all the impulses are delivered, and. the line relay 128 returns to `its operated position, the circuit through the relay 134 becomes broken, thus permitting the springs 212 and 209 to return to normal position.

` springs 212 and 213 disengage, the. circuit through the private magnet 135 becomes broken, whereby the said magnet denergizes, permitting the side switch toV pass .from first to second position. The calling subscriber now operates the dial for the last digitI 1, and again the line relay 128 is deenergized; but when the spring 196 engages the spring 197, an energizing circuit is established through'the `rotary magnet 132 instead of through the vertical magnet 131.

This circuit extends fromr ground G11 through the springs 196 and 197, springs 199 and 201, conductor 208, springs 214 and 215, through the winding of the rotary magnet 132, contact point 216, side switch wiper 140 to the battery lead 157, thence through battery B to ground G. r1`he rotary magnet. upon energizing operates to give the shaft and shat't wipers 125, 126 and 127 one rotary step, and to carry said wipers intoengageinent with the first bank contact of the second level, from which contact the normal conductors 217 and 218 extend to a trunk line leading lto the desired oitice. Also. when the line relay 128 "denergized for the last digit, and placed lthe springs 196 and 197 in Contact, an energizing circuit was established through the private magnet relay 134ias before. The relay 134, upon energizing, again closes the circuit through the private magnet 135 when the springs 212 and 213 engage, and when the relay returns to its energized position the circuit through the private magnet relay 134 vis again broken, and the1 circuit through the p'rivate magnet 135 is in turn also broken it' the first trunk line is idle. The side switch, therefore, passes from second to third position. lhen the side switch wiper 4 vcalled subscriber.

ringer generator H across the lineV of the The energizing circuit throughthe ringer relay 145 extends from ground G1* through the interrupter 144, springs 220 and 221,-ringer relay 145, contact point 219, side switch-wiper 140 to the battery lead 157, thence through battery f B to ground Gr. iVhen the connector side switch passes to third position, and the side switch wiper 138 engages the grounded contact point 222, a guarding potential is established at the connector private bank to protect the 'seized line against interference by other calling subscribers. This potential eX- tends -from ground G15 to the contact point 222, side switch wiper 138, to the shaft private wiper 127 which engages the private contact of the called line, and to the multiple private contacts of the. called line. Also, when the side switch wiper 138l engages the grounded contact point 222, an energizing circuitis established through the cut-ofi1 relay ot the line switch C. This circuit extends from ground G15 through'the side switch wiper 138 to the shaft private Wiper 127, conductor 224, through the Winding of the cut-,off relay 223 to the battery lead 157,

f thence through battery B to ground G. |The ringer relay 145, being intern'iittently energized by the intei'i'upter 144, signaling current is intermittently sent to the called substation A" from the ringer ygenerator H through the springs 225 and 226, side switch wiper 136, contact point 227 shaft wiper 125, normal conductor 217, line conductor-228, ringer 229 and condenser 230, through the springs 231 and to the line conductor 233, normal conductor 218, shaft wiper 126, contact point 234, side switch wiper 137, and through the ringer relay springs 235'and 236 back to the ringer generator H. In response to the signal the called subscriber removes the rcceiver 237 from the switch hook 238, whereby the spring 232 engages the spring 239, thus bridging the primary circuit, including the transmitter 240 in series with the primary winding 241, across theline conductors 228 and 233. lVhen the primary circuit comes across the line an energizing circuit is established through the relay 141 of the connector F, said circuit extending from ground (irla to the side switch wiper 138, winding 143 of the relay 141, thence through the ringer relay springs 242 and side switch wiper 137, contact pointI 234, shaft wiper 126. conductors 218 and 233, springs 232 and 239, impulse springs 243. primary winding 241, transmitter 240, through the conductors and 217, shaft wiper 125, side switch wiper 136, ringer. relay springs 226 and 244, winding 142 of the relay 141 to the battery ,lead 157, thence through battery B to ground G. The relay 141 thereupon energizes and separates the i Switch springs220 'and 221, whereby the intermittent circuit through the ringer relay 145 becomes permanently broken.` The two substations A and A are-now connected over ythe circuits shown by the heavy line conductors in Figs. 1 and 2, the substation A receiving battery current for talking purposes through theline relay 128, while the substation i receives current for talking purposes through the relay 141. In the preceding it was assumed that the first trunk line, of which there are several, leading to the desired otlice was not busv. It will now be pointed out how the connector switch F operates, it the first trunk line is busy, to automatically select the first idle trunk line.

-when the rotary magnet 132 operates fol' Vthe last digit l, the private shaft wiper 12'( comes into engagement with the first bank contact, which, it will be assumed, is protected by a guarding potential. In that event an energizing circuit is established through the private wiper relay 146. This Circuit extends from the grounded terminal G of the battery B through an occupying (not shown), through the bank con- Dtact, through the shaft Wiper 127, side switch wiper 138, contact point 246 (the side switch being in second position), through the winding of the private wiper relay 146 to the battery lead 157, thence through battery B to ground G. The relay 146 thereupon energizes and presses the springs 247 and 248 into contact, closing an energizing circuit through the private magnet 135, said circuit extending from ground Gr16 through the springs 247 and 24S, through the private magnet 135 to the battery lead, thence through `battery B to ground G.

Then the rotary magnet was energized for the last digit the private magnet relay 134 was also energized, being in multiple with it. When thus energized the relay 134 acts as before-to close the private magnet circuit, and also to change the energizing circuit of the rotarymagnet. The new energizing circuit for the rotary magnet extends from ground G through springs 196 and 197, springs 199 and 201, conductor 208 as before, through springs 209 and 211, rotary magnet 132, eontact'point 216, side switch wiper 140 to the battery lead 157. Thus, while the impulses are being delivered, the private magnet relay 134, being slow acting, remains inf an operated position. But as soon'as th impulses are delivered the relay 134 denergizes. As previously assumed, it the first trunk is idle the private magnet 135 will be denergized by the operation of the private magnet relay ;l but if `the trunk is busy, as assumed in this instance, the private relay 146 is energized. This relay closes the Acircut of the private magnet 135 before the latter has been denergized by the opening of its circuit at the relay 134. Therefore,

the last busy trunk line.

the private magnet continues in an energized condition until thc private wiper relay is deenergized, and it in turn is not denergized until the private wiper is rotated onto a non-grounded contact point. lVhen the private magnet relay 134 dcinergizes and the private magnet 135 is still held energized, a new energizing circuit is closed through the rotary magnet 132 and its interruptcr springs 249'. This circuit extends trom ground G13 through the interrupter springs 249, private magnet springs 250 and 251, private magnet relay springs 210 and 20S), through the winding ot' the rotary magnet 132, contact point 216, side switch wiper 14() to the battery lead 157thence through battery B to ground G. The rotary magnet 132 now continues to rotate automatically and carry the shaft wipers 125, 126 and 127 past As soon as the private wiper 127 engages the contact point upon which there is no guarding potential, the energizing circuit through the private wiper relay 146 is broken, whereby the springs 247 and 248 disengage and in turn break the cncrgizingcircuit for the private magnet 135, which now permits the side switch wipers tov pass from second to third position. In this manner the connector switch automatically rotates to select an idle trunk line out of the group leading to` the desired oiice. It', however, all of the trunk lines allotted to the desired office arel busy. the shaft wipers are automatically rotated to the contact points 252, 253 and 254. 100 It will be noted that the private contact 254 is insulated or cut ofi' from the corresponding private contacts in the other rotary connector banks, so that, when the Wiper 127, reaches this Contact, the 146 is deinergized, which in turn denergizes the private magnet 135, which in turn opens the rotary magnet circuit permanently and releases the, side switch to third position. When the side switch, wipers pass to their 11o respective third positions, an energizing circuit is closed through the relays 141 and 154. This circuit extends from ground (l17 through the busy relay154, bank contact 252, shaft wiper 125, contact point 227, side 115 switch wiper 136,` ringer relay springs 226 and 244, through the winding 142 of the back bridge relay to the battery lead, thence through battery B to ground G. The relay 141 thereupon energizes and opens the ringer 120 magnet circuit, whichwas closed for an in stant when the side switch passed to third position. The relay 154, upon energizing, presses the springs 153 and 255 into Contact, whereby the busy-signaling apparatus I is 125 connected with the rotary shaft wiper 126, and a busy-signaling current is sent to the calling subscriber in the usual manner. The release of the central oflice switching apparatus is brought about when the calling subv 130 private wiper relay wherebyI the energizing scriber restores the receiver 2 to the switch lhook 3, whereby the spring 17 is pressed out 'and 200 to the release magnet 133, normal springs v1551 and 132 andto the battery lead 157, thence through battery ll to ground G. The release magnety 133, upon energizing, operates in the usual manner to restore the connector switch shaft and side switch'to normal position. Vhen the switch shaftl returns to normal position the normal arm 256 carries the normal spring 1311out of engagement with the normal spring 132".

whereby the energizing circuit through ,the release magnet 13S is broken. Also. when the relay 128 deenergizes, the ground potential at the trunk conductor 191 is removed. and in turn the energizing circuit through the release relays 121 and 112 of the selector switches E and D is broken. YThese relays return to normal position and in turn close an energizing circuit through their respective release magnets. The energizing circuit through the release magnet 121 ot the selector switch E extendsV from ground (lT through the springs 171 and 175,'springs 177 and 178, through the release magnet 121. normal springs Q57 and 258 to the battery lead 157. thence through battery B to ground G. The release magnet thereupon energizes and attracts its armature, whereby the shaft wipers and side switch are restored to normal position in the same manner as in the. connector switch: also,when the switchshatt returns to normal "position the normal arni 256 carries the normal spring `257 out ot engageipent with the Contact point Q56.

Y circuit through the release magnet 121 becomes broken. The circuit throu'gli the release magnet 10S of the selector switch l) extends from ground G" `through the springs 161 and 166. release relay springs 163 and 164.' through the re lease magnet 106. normal springs 110 and 111 to the battery lead 157. thence through battery B to ground (l. rThe release magnet 10Sthcieupon energizes and attracts its armature. whereby the switch Ashatt and side switch are also restored to normal position. As in the preceding switches. the normal arm 10) separatesthe normal springs 1.1().and 111, whereby the energizing circuit through the release magnet 16S becomes broken.

Furthermore. when the release relay112 deenergizes and permits the spring 165% to engage the spring 16%, an energizing circuit ,is established through the back-release rein position to be released upon the subi sequent deiinergization of said magnet. The

back-release relay 113, upon energizing. disengages the springs 260 and 61, whereby the energizing circuit through the release,

magnet. 21 is broken, thus permitting the line v switch C to return to normal position.

In the foregoing itv has been shown how selector switches l) and E and the rotary connector switch F, operates to establish connectioii with a desired lino. 1ty will now be shown how the central ottico selector switches y and connector switch L operate to establish a ldesired connection with one of the group of lines on the tenth level. Since it has been assumed that the connector L is connected to the fourth level ot the second selector banks, the number ofthe tirst group of lines ending in the tenth level ot said connector L will be 2401. ln calling the number '21.01 the operation of the lino switch C, master switch J, tirst selector D and second selector l@ is exactly the same as when #2221. was lalled. except that the second selector E receives `tour impulses instead ot' two and thus selects an idle connector L 4instead ot F. Vihcn the connection is thus exteiidedto the connector L the line relay 276 and release relay 282 are energized in the. manner explained for the relays'lZS and 133 of the connector l". When the calling device at substation A is operated for the third digit 0 the impulse springs are t'orced out ot` engageii'ient ten times in the usual manner, thus opening the energizing circuit of the line relay 270 ten times. Each time-the rclay Q7() denergizes, the spring engages spring whereby an energizing circuit is closed extending from ground G through springs-.263 and 285, Q87 and '266. private magnet relay "286.

'vertical,magnet 268 and las side switch wiper i272 to battery. The vertical magnet `266 receives ten impulsesy over the circuitjust traced and operates to raise the wipers '265. '266 and 267 to a position opposite-thc tenth bank level. As soon as the switch shaft is raised the rst step the arm 289. which is attached to said shaft, permits the otlnormal springs 290 and 291 to enl gage. whereby the release magnet Q77 is connected with the battery B. Before the switch shaft reaches the upper limit of its travel,-that is, with the Wipers 265, 266, and 267 standing opposite the tenth levl, the arm 289 forces the springs 292 and 2'93 out of engagement with the springs 294 and 295, respectively, and forces spring 293 into engagement with spring 296. The separation of springs 292 and 294 disconnects the private magnet relay spring 2962l from the private magnet spring 297 which form part of a locking circuit for the relay 298 when a busy line is called on any of the'first nine levels. 'The shifting of spring 293 shifts the connection of the contact point 299 of the sideswitch Wiper 273, to the relay 278. The private magnet relay 288, which is included in the circuit of the vertical magnet 268, energizes upon the first impulse t0 that magnet and, being slow-acting, remains in its operated position until after the last impulse. When the private magnet relay 288 energizes, it closes an energizing circuit extending from ground G1 through springs 300 and 301 and private magnet 276 to battery. After the last impulse to the vertical magnet the private magnet relay 288 deenergizes and opens the energizing circuit of the private magnet 27 6, whereupon the said private magnet denergizes and permits the side switch to pass to second position. lfVhen the side switch wiper 272 passes from first? to second position it shifts the battery connection from the vertical magnet to the rotary magnet 269. Vhen the calling device is operated for the last digit 1) the line relay 270 is4 deenergized once in the usual manner, and operates to close an energizing circuit through the rotary magnet 269. This energizing circuit extends from ground G18 through springs 283 and 285, 286 and 287, relay 288, springs 302 and 303, and through the rotary magnet 269 to battery B. The rotary magnet responds to this impulse to rotate the shaft wipers onto the first set-of contacts of the tenth level. The private magnet relay 288 is also energized by this impulse and again closes the energizing circuit of the p'rivate magnet 27 6. When the private magnet relay denergizes after this impulse to the rotary magnet, it opens the circuit of the private magnet 276, which thereupon' denergizes, if the first line is idle, and permits the side switch to pass to third position, thus completing the connection. If, however, the first line of the group #2401 is busy, there will be a guarding ground potential on the private bank contact 304, and when the wiper 266 strikes this grounded contact a locking circuit is closed through the private rmagnet 276, independently of the relay 288.

This locking circuit extends from ground ythrough some otherI occupying switch (not shown) `to the private bank contact I thence through private wipeu 266, relay springs 307 and 308, side switch wiper 273, contact point 299, springs 293 and 296, relay 278, and private magnet 276 to battery B. The private magnet thus remains energized and the side switch locked in second position as long as the-wipers remain on the first busy bank contacts, even though the private magnet relay 288 Adenergizes.shortlyafter the first impulse to the rotary magnet. The relay 278, which was 'included in the locking circuit just traced through private magnet, energizes and' forces the spring 309 into engagement with spring 310. The engagement of springs 309 and 310 completes a. connection between the interrupter 279 and rotary magnet 269. The rotary magnet then re ceives one impulse .from the interrupter 279. and advances the shaft wipers to the` second line of the group #2401. If this second line is also busy, the private wiper 266 finds another grounded contact, and maintains the energizing circuit of the relay 278 and the private magnet 276, whereupon the rotary magnet will receive another impulse to cause it to rotate the wipers another step. This automatic rotation of the wipers will continue until an-idle line is reached, or, in case all the lines of the group are busy, the wipers will be rotated onto the contacts 311, 312 and 313. The private wiper, finding no ground at contact 313, will permit the relay 278 and private magnet 276 to denergize. r1`he denergization of the relay 278 disconnects the interrupter 279 from the rotary magnet 269, and the denergization of the private magnet permitsthe side switch to pass to third position, whereupon the calling subscriber will receive the busy-signal in -the manner explained with reference to the connector F. It has been assumed here, however, that the second line of the group is idle. In this case, when the private wiper 266 passes from the contact 304 the relay 278 and private magnet 276 are denergized. rl`he deinergization of the relay 278 disconnects the interrupter from the rotary magnet, as before explained, and the private magnet allows the side switch to pass to third position. 1Vhen the side switch of the connector L passes to third position the connection is completed to the called substation and the bells are rung in the manner explained in connection with the connector F'. Also, in this instance, as in the previous one, the removal of the receiver at the called substation causes the energization of the backbridge relay, which opens the circuit of the ringer relay 315. The energization of the back-bridge relay 314 also opens the short: circuit around the resistance 332 by separating the springs 321 and 322, thus including thisresistance in theholding circuit of the release relays 112, 124 and 282 of the switches neoted to one of the first nine levels of the connector L, as, for instance, #24:41, the operation of the central'oiice switching mecha nism is the same for the irst three digits as thatexplained in the preceding case, with theexeeption that the switch shaft is raised only four steps, and consequently the springs 292 and 293 are not operated by the arm 289.

When the calling device is operated for the last digit the rotary magnet 269 receives one impulse, rotates the Wipers onto the first contact, and if the called line is idle the side switch is tripped to third position, in the manner explained when it was assumed that the first line of the group 2401 was idle. If', however, the line 2441 is busy when called, the Wipers are not automatically rotated to the next contacts, but remain in engagement With the line #2441, and the side svvi-tch is locked in second position, thus preventing the completion of the connection to the busy, line, and giving the callinef subscriber the busy-signal. The manner in Which the side switch is locked when a busy line is encountered is as follows: /Vhenever a. line is 'i busy the private connector bank contacts AWith spring viously traced,

of that line are provided with a guarding ground potential. Thus, when the Wipers are rotated to a busy line, and since the side switch is in second position, this ground potential is extended fronrthe private `bank contact over wiper 266, relay springs 307 and 308, side switch Wiper 273, contact point 299,

springs 293 and 295, side switch Wiper 275,

ringer relay springs 316 and 317 and Winding 818 of' back-bridge relay 3H to the bat-V tery B. The relay 314: thereupon energizes and 'by forcing spring 320 into engagement 319 closes a locking circuit through theprivate magnet 276. This locking circuit extends from the grounded private bank' contact to the spring 295, as preand thence through y'the springs 319 and 320 and private magnet 276 to battery. This locking circuit for the private magnet is established as soon as the wiper reach the busy line, and before the private magnet relay 288 has -time to denerf gize. The relay 288 denergizes inthe usual manner after tlie last rotary impulse, and as the private magnet now remains energized a energizing, shifts the spring 308 out of engagement with spring 307 and into engagement with the spring 525, whereby the lockf 'ing ground ofthe relav 314 and private magnet 276is transferred from the private bank contact to ground G20; This shifting of the locking ground is for the purpose of maining the rotary magnet 269 from the impulsespring 285, so that the said magnetwvill not be energized when the receiver at the calling substation is restored to the switch hook.

While the private magnet 27 6 .is thus. energizedit locks the side switch in second position to prevent the completion of the con-- the busy-signaling machine I with the calling'line by Way of the springs 327 and 328,-

side switch Wiper 27st and condenser 2,81. VWhen a busy line has been called, the connectorL and selectors D and E are released nection with the busy line, and also connects by the restoration of the receiver to the switch hook in the same manner connector F was released.

In the description of the operation of the connector F it was explained how the .group of trunk lines corresponding to number 2221 might comprise three trunks, the `fourth set of bank contacts reserved for giving the busy signal in case all three trunksy are busy. Vith this arrangement thnext group of trunks in the second level would be reached by calling the number 2225. The five impulses for the digit 5 would cause the connector Wipers to be rotated five steps over the three trunks and the blank set of contactsy of the first in thelsecond level beingy that the group to the first trunk of the second group.

If this trunk is busy the Wipers then begin ,to advance automatically -to find an idle trunk in the group after the last impulse from the substation is delivered. Thus it is evident that each bank level of these connectors may accommodate more than one group of lines. the first idle line of any group being accessible by calling the number corresponding to the position of the bank contacts of the first line in the group. Likewise, in the Connector L each level in which the automatic rotaryvfeature is provided may accommodate more than a single group of trunk lines. In the case assumed herein the next group in the tenth level would be numbered M05.' Y f IFrom the foregoing it will be seen that I provide rotary connectors, F and L, for example. which are controllable over metallic line circuits. In this way these rotary connectors are controllable without the necessity of grounding the lines at the substations. Heretofore all rotary connectors, so tar as I am now aware, have been controlled by grounding lthe line at the. calling substation, or at the operators position. depending upon g,he charm-.ter of the system, lilith in v im- .mshing talking current over the subscribers lines to the substations thereof. For some of the broader purposes of my invention, however, the common battery feature 1s not necessary, and the first selectors may be given other arrangements. As illustrated, the rotary connector F is rotary in all levels thereof, so that if all of the trunk lines of any particular group are busy the calling `trunk lines are connected subscriber will automatically receive the busy-signal in the manner explained. The rotary connector L, however, is of such character that it may bel rotary in one or more levels, and then operate like an ordinary connector in the other level or levels. The wipers of either of the connectors F or L may be rotated to any desired contact'in their respective bank levels by impulses from the calling stationfthe automatic rotation taking )lace only after the last impulse has been delivered. .This cnnector L is, therefore, equipped with a discriminating busytest apparatusthat is to say,v a busy-test apparatus which willdiscriminate between busy trunk lines and busy single telephone lines. By this I mean that the busy test is of a discriminating nature, inasmuch as when a trunk ,line tests busy the connector does one thing and when a single subscribers line tests busy the connector does scriber recelves. the busy-signal.` When a single subscribers line tests busy this same connector then remains locked on that line, .and the calling subscriber receives the busy,- signal-that is, assuming, of course, that the single subscribers lines are connected to the bank levels upon which the connector L operates as an ordinary connector, and that the which the switch acts as a rotary connector, as has been previously pointed out. Thus 0- the connector is capable of discriminating 6 between busy trunk lines and busy single lines, operating in one Way when it finds a busy trunk line. and operating in quite a different way whcn it encounters a busy Single liuc. This, as explained, is all accomplished in a svstcm in which the switches are conto the levels upon' trolled over metallic line circuits. In this way rotary connectors are controlled and operated without the necessity of grounding the line at the calling substation.

vWhat I claim as my invention is zl. In a. telephone exchan e system, the combination with subscribers telephones, a line individual to each telephone, a line` switching device having line terminals and a group of trunk terminals, of a moving contact member for said switching device, automatic means for stepping said member to any of said line terminals or the first trunk terminal of said group, means actuated in case said first trunk is busy for steppingusaid 80 member to a terminal of an idle trunk line, said switching device operated over a circuit including both sides of any one of said lines in series, said circuit passing through the subscribers telephone instrument.

2. In a telephone exchange system, the combination .with a telephone line extending from a substation to a central oHice individual to a subscriber, of a connecting circuit at the central ofiice, a progressively vmovable connect-ion -switch for uniting said connecting circuit with the` telephone line, a line switching device having terminals of lines in the exchange, trunk lines leading to terminals of said device, a contact.arna for said device adapted to sweep over said terminals to unite said connecting circuit with said terminals, automatically operated mechanism for advancing said arm over said terminals and over sald trunk terminals until an idle trunk line is reached, a busy Signal, means actuated in :ase all of said trunk lines are busy for applying said busysignal to said connecting'cincuit, a-relay individual to said device, said relay energized over both sides of said line in series for operating said switching device, a receiver switch hook vat said telephone, said relay circuit controlled thereby.

In a telephone system, a calling subscribers telephone, aline individual thereto, the 'combination of a plu 'ality of telephone lines running to the same'substation, telephones on said lines, an automatic switch provided with means for extending connection from said calling line to any one of said telephone lines, automatic means 'for causing the operation of said switch to select the first idle one of said lines, a common batter relays allotted to said switch and controlling 2 the flow ot talking current from said battery to the called telephone line, and a circuit over which the said switching means is controlled comprising the two sides of said subscribers line circuit in s'eries.

4. In a telephone system, a calling subscribers telephone, a line individual thereto, a plurality ot' lines any one of which will serve the purpose of a calling subscriber, means including an automatic switch common toa plurality of said lines forfautomatically selecting an idle line for the caling subscriber, means controlled at said automatic switch for supplyingf all the talking curient'to a' subscribers substation, and a metallic line circuitp'ver which the said` arrela'y individual thereto through the me- 'dium o'which said substation control is eX- .,ercised, said-relay energized over both corr" .25 .ductors in any one of said telephone lines in f'series, said relay circuit including a Vswitch l iitthe telephone' directly operated by the /rsivitch hook.

l arl 6. In a telephone system, a connector, a

"relay, trunklv lines leading from said connec- 'tor, t2-calling substation, a line circuit indi- Y 'vidual thereto, means for transmitting cur- .'rent over two/sides of said line circuit in series tosaid relay to operate said connector Slin accordance with the last two digitsof the,

called n iimber, a receiver switch hook, a switch at said telephone directly controlled Vby said hook, said switch included in the cirf ,cuit of said relay, said connector provided l0 lwith means for automaticaly selecting an idle trunk line, and means for transmitting l a busy-signal over said line circuit if all 'the ,f trunk lines are busy.

i 7 vIn arch-,phone system, a telephone station, a lin'e circuit individual thereto, means for transmitting calling current over the two sideis-osaidI circuit in series, a connector responsive to' said current, lines leading from ",said connector, means whereby when the connector finds one of said lines busy it auto- .,natically passes to the-next line, and means whereby when the connector inds another line busy it may stop and go no farther, a reilay for operating said connector, a receiver 1I-switch hook, a switch at said station operater'llby said hook, said switch included in the`-circuit of said relay.

I n a telephone system, a telepho-ne station, aline circuit individual thereto, means 30' for transmitting current over said circuit, a bank of" contacts, lines leading from said contacts;l a wiper adapted to engage sai contactsy' mechanism for actuating said wiper, a relay operated over two sides of said Se circuit in series for operating said'mechanism, means for preventing` said wiper from passing a busy called line, and means Jfor causing said wiper to automatically select an idle line, a receiver switch hook, a switch at said station operated by said hook, said switch included in the circuit of said relay.

9. In a telephone system, a `telephone station, a line circuit individual thereto, a stepby-step mechanism, a plurality of lines divided into two groups, meansincluding a relay whereby said mechanism is operated over two sides of said line circuit in series to select a certain called line .from one group whether idlev or busy, and means whereby said mechanism is operative to automatically select an idle one of the lines in the other group, areceiver switch hook, a' switch at said station operated by4 said hook, the circuit of said relay including said switch. f 85 10.` In a telephonesystem, a telephone station, a line circuit individual thereto, tele'- phone lines, other lines, switching means including a relay responsive to current sent over two sides of said line circuitin series Q0 for testing the lines, means for causingfone kind of operation of said switching-means when a telephoneline tests busy, and means for causing another kind of operation when one of said other lines tests busy, a receiver switch hook, a switch at said station operated by said hook, said switch included in the circuit of said relay.

11. In a telephone system, a telephone station, a line circuit individual thereto, a connector having a relay operated over two sides of said line circuit in series, said connector having a plurality'of parallel planes of operation, means whereby said connector is automatically operative in o'iieor more 105; of said planes to automatically select anV idle line, and means whereby said connector is operative under substation control in one'or more of the planes, a receiver switch hook, a switch at said station operated by v11`0 said hook, said switch included in the circuit of said relay.

12. Ina telephone system, suitable lines, a telephone station, a line circuit individual thereto, a connector having a plurality of parallel planes of operation under manual control, and means whereby said connector is operative automatically in one of said planes to automatically select an idle line,

a relay operable over two sides of said line circuit in series for operating said connector, a receiver switch hook, a switch at said stationA operated by said hook, said relay` included in the circuit of saidl switch.

13. In a telephone system, telephone lilies, 4125 trunk lines, a connector, a telephone station,

d a line circuit individual thereto, a relay roil operating said connector, means'for transmitting calling current overtwo sides of said circuit in series to said relay to operate automatically said connector, said connector having mechanism operative under substation control to find a called telephone line, means whereby said connector is operative to automatically select an idle trunk line, means for insuring a busy-signal if the called telephone line is usy, means for insuring a like signal if' all the trunk lines are busy, a receiver switch hook, aswitch at said station operated by said hook, said relay included in the circuit of said switch, means including first selec tois for reaching said connector, and means for automatically' selecting idle first selectors, said selectors controllable over the said metallic circuit in accordance with the first digit of" the called number.

In a telephone system, a connector, a relay, trunk lines leading from said connector, a telephone station, a line ciicuit individual thereto, means for transmit-ting current over two sides of said circuit in se-v ries to said relay to operate said connector in accordance with the last two digits of the called number, said connector provided with means for automatically selecting an idle trunk line, means f'or transmitting a busysignal over said metallic circuit if all the trunk lines are busy, a receiver switch hoo-k, a switch at said station operated by said hook, said relay included in the circuit of said switch, means including first selectors for reaching said connector, andineans for lautomatically selecting idle first selectors,

said selectors controllable over the two sides of said line circuit in accordance with the first digit of the called number.

15. In a telephone system, a telephone station, a line circuit individual thereto, means for transmitting calling current over two sides of said circuit in series, a connector having a relay responsive to said current, lines leading from said connector` means whereby when the connector finds one of said lines busy it automatically passes to the next line, means whereby when the connector `finds another line busy it may stop and go no farther, a receiver switch hook, a switch at said station operated by said hook, said relay included in thev circuit of said switch, means including first selectors for reaching said connector, and means for selecting idle first selectors, said selectors controllable over the two sides of said line circuit in accordance with the first digit of the called number.

16. In a telephone system, a circuit individual thereto` an line. a liiic automatic switch opeiative o'vcr two sides oi said line circuit'in series in accordance with the last digits of" the called number, one or more grounded private bank contacts and a non-v grounded private bank contact for said switch for controlling said switch. means under thc control of a subscriber for moving said switch over certain of said groundl grounded contacts.

ed contacts, and means for automatically moving said switch over other of said 17. Ina telephone system, a line, a line circuit individual thereto, an automatic switch, a rotary magnet therefor controlled over two sides of said line circuit in series in accordance with the last digit of the called number, a plurality of grounded and non-grounded bank contacts for controlling said operation, and means for energizing said rotary magnet when connection is made with a grounded contact of said bank.

1S. In a telephone exchange system, the combination with a line switching device having' line terminals and a group of trunk terminals, of a moving contact member for said switching device, automatic means includinga relay for stepping said member to any of said line terminals or the first trunk terminal of' said group, means actuated in case said first trunk is busy for stepping said member to a terminal of an idle trunk line, a line circuit over two sides'in Series of which the said switching device is `operated,van il means at the central station including said relay for supplying talking current over said circuit.

19. In a telephone exchange system, the combination with a telephone line extending from a sub-station to a central office, of a connecting circuit at the central office, a connection switch for uniting said connecting circuit with the telephone line, a line switching device having terminals for lines in the exchange, a relay for operating said device, trunk lines leading to terminals of said device, a contact arm for said device adapted to sweep over said terminals to imite said connecting circuit with said terminals, automatically operated mechanism for advancing said arm over said line terminals and for' automatically advancing said arm over said trunk terminals until an idle trunk line is reached, a busy signal, means actuated in case all of said trunk lines are busy ,for applyingsaid busy-signal to said connecting circuit, a line circuit over two sidesin series of which the said .relay isoperated, and means at the central

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